1. Field of the Invention
This invention relates to a sewing machine, more particularly to a stationary thread-cutting device for a sewing machine, which guides and cuts a bobbin thread adjacent to a front side edge of a needle plate.
2. Description of the Related Art
In U.S. Pat. No. 7,021,226 B2, the applicant disclosed a sewing machine 1 as shown in FIGS. 1 and 2. The sewing machine 1 includes a needle plate 13 with a cutout part 131 which opens at a lateral edge 132, and a guide plate 14 connected to a bottom side of the needle plate 13 and extending across the cutout part 131. The guide plate 14 has two slide rails 141, an opening 142 corresponding in position to a bobbin holder 11 that holds a bobbin 17, and an arc-shaped thread guiding slot 143 having one end communicated with the opening 142 and another end extending to one of the slide rails 141. A slide cover 15 covers the cutout part 131 and is slidable along the slide rails 141. A thread guiding groove 12 is disposed along one of the slide rails 141 adjacent to the arc-shaped thread guiding slot 143, and has one end connected to the thread guiding slot 143 and another end extending to the lateral edge 132 of the needle plate 13. A cutter 16 includes a cutter blade 161 which is fixed to the bottom side of the needle plate 13 proximate to the lateral edge 132 and the thread guiding groove 12, and which extends across a cutter groove 133 formed in the lateral edge 132.
Since the cutter 16 is mounted at the lateral edge 132 of the needle plate 13, when it is desired to obtain an appropriate length of bobbin thread for interlacing with a needle thread (not shown) for stitching a fabric piece, bobbin thread is drawn from the bobbin 17 held in the bobbin holder 11, is passed through the thread guiding slot 143, a thread tensioning unit (not shown) mounted on the bobbin holder 11, and the thread guiding groove 12, and is pulled into the cutter groove 133 for cutting by the cutter blade 161. However, since the thread guiding groove 12 extends along the slide rail 141, manual threading of the bobbin thread along the thread guiding groove 12 after the bobbin thread is passed through the thread guiding slot 143 is difficult and troublesome. Improvement in this respect is therefore needed. Moreover, it is desirable to improve the aforesaid sewing machine to shorten the required length of the bobbin thread drawn from the bobbin while ensuring good stitching quality.